Composition of matter and method of treating fibrous cellulosic materials therewith



This invention relates to a composition of matter that is useful primarily in the treatment of paper, cardboard, corrugated board and other porous cellulosic sheet materials for rendering them impermeable and resistant to water, to the treatment of such material for impregnation therewith and to the material so obtained.

The art relating to the treatment of paper and other cellulosic sheet materials, particularly corrugated paper board, for rendering these sheets impermeable to the penetration of water is replete with suggestions for accomplishing these results. Some of the methods heretofore proposed are applicable only to certain types of fibrous sheet materials. Others are too expensive to be commercially feasible and still others leave much to be desired in the effects they produce. Thus, for example, many methods of treatment produce paper with a waxy coating that will readily peel off or be scratched off. Others make the paper non-receptive to ink and therefore capable of bearing printed matter such as addresses or advertising matter. Still others lose appreciable rigidity and strength under severe humidity conditions, such as ice cooling, and become stained and discolored.

In accordance with the present invention, an inexpensive composition of matter and method of treating fibrous sheet material therewith are provided for producing a fibrous sheet material of excellent quality, dimensional stability under varying humidity conditions, resistance to penetration by water, resistance to peeling and cracking and at the same time, a most satisfactory ability to accept and retain organic ink and other marking materials utilizing organic solvents or dispersants. If desired, resistance to fats, oils and the like may also be increased.

The treatment in accordance with the invention has no adverse effect on printed matter applied to the material before treatment, or upon glued connections. It can be applied to one or both sides of the sheet mate rial and the treated material can be glued or cemented as effectively as untreated sheet material or material otherwise treated. The treatment increases the wet strength and dimensional stability of paper and paper board tremendously and produces a significant increase in the dry strength thereof as well. The original color of the sheet material is not affected and no unpleasant odors are imparted to it by the treatment. The treatment can be applied to fiat or shaped material, e.g., to flat corrugated paper board such as that normally employed in the container industry, or to cartons made therefrom.

The composition of the present invention is a mixture that can be vaporized under the conditions of operation and comprises essentially a low molecular weight chlorinated hydrocarbon and benzene and preferably also a waxy component.

The chlorinated hydrocarbon component is believed to have the function primarily of effecting penetration of the fibrous sheet material and swelling the fibers thereof. It may be any chlorinated hydrocarbon, or combination thereof, that is capable of volatilizing under the conditions of operation and that is soluble in benzene. For most effective results, the chlorinated hydrocarbon should contain at least two chlorine atoms in the moleatet lice 3,@Z,l5? Patented Feb. 6, 1962 cule and should have a boiling point between about 35 and 160 C., preferably at about C. Prominent among these are particularly the hydrocarbons containing two carbon atoms, e.g., trichloroand tetrachloroor perchloroethylene (CHCl=CCl and CCl CCl Chlorinated hydrocarbons having a single carbon atom, such as carbon tetrachloride (CCl and chlorinated hydrocarbons containing three or more carbon atoms, such as chloropropanes and chloropropenes may also be employed in whole or in part but generally do not have as desirable a combination of penetrating, volatilization, non-toxicity, non-flammability and odor properties as the chloroethylenes and chloroethanes.

Carbon tetrachloride (CCl while useable, is not recommended unless precautions are taken to avoid injury to the health of the workmen applying the composition to the fibrous sheet material because of the toxicity of the gases. The dichloroethylenes (CH =CCl and CHCl=CHCl), while capable of leading to the prepar-ation of fibrous sheet material having a smooth, hard surface of generally good appearance, must be used with caution because of their inflammability.

Benzene, as the second essential component of the composition, has the function of dissolving the waxy component, if any, and of assisting in swelling the fibers. Longer chain aliphatic compounds and mixtures such as kerosene, gasoline and the like are operable but are considered undesirable because they impart a greasy feel, an unpleasant odor and a yellowish color to the material to which they are applied.

A portion of the benzene component may, bereplaced by a chlorinated benzene. Monochlorobenzene and dichlorobenzene are operable and may be used in amounts up to about 8% by weight of the benzene component. They are not generally preferred because of their strong and persistent odor and high cost. They volatilize relatively slowly and their strong odor remains too long after treatment for most purposes. When used in conjunction with carbon tetrachloride, their flammability can be overcome but the treated sheet tends to have a rough surface. The trichlorobenzenes and tetrachlorobenzenes, having boiling points ranging from 172 to 219 C., may be used in amounts up to about 25% by weight of the benzene component. They are not flammable or toxic and create less difficulty than monoand dichlorobenzenes in the uniform application and penetration of the cellulosic sheet.

The waxy component may be any vegetable or mineral wax, paraffin wax being preferred.

The relative proportions of the essential components of the mixture may vary considerably depending upon the particular results desired and the economics involved in the end use of the treated product. The proportion of the chlorinated hydrocarbon component may be as low as about 40% and about as high as about 94% by weight, depending primarily on the amount of benzene component that is employed, the cost of the chlorinated hydrocarbon component and the initial porosity of the fibrous sheet material. The lower the initial porosity and the greater the diificulty of penetration, the higher should be the relative proportion of chlorinated hydrocarbon component. The proportion of the benzene component may vary from as little as 6% by weight to as high as about 5%. by weight, depending in part upon the identity of the chlorinated hydrocarbon component and upon the economies of the process. When the chlorinated hydrocarbon is expensive and contains a large proportion of chlorine atoms, the benzene component may be present in as much as 50% by weight, e.g., with perchloroethylene, or about 40% by weight with trichloroethylene.

The presence of a waxy component is not absolutely necessary in the composition of the invention when it is if desired,

to be applied to material having a 100% cellulosic content, especially of long cellulose fibers. The relative proportions of chlorinated hydrocarbon and benzene components are preferably, in the absence of such a waxy component, about 60 and 40% by weight, respectively. It is generally highly desirable, however, depending upon the porosity of the fibrous sheet material and the degree of water impermeability desired, to include up to about 22% by Weight waxy component in the composition of the invention. Generally speaking, amounts in the neighborhood of about 10% are ample for paper or paper board of reasonably good grade.

It is also within the scope of the invention and desirable, as optional ingredients in the mixture of the invention, to employ a minor amount, e.'g., up to about 2% by weight, of a pine resin, other vegetable resin or nonoxidizing alkyd resin and a trace, i.e., a few drops, preferably about two drops per 1000 grams of mixture, of castor oil to act as a plasticizer. The resin contributes to a desirable hardening of the paper and may be colophony, shellac or other similar resin. It is generally undesirable to use more than the specified amount of resin because excesses over 2% tend to darken the paper.

It is believed that when paper or paper board is treated with the composition and by the method of the invention, the individual fibers are swollen so that they grip one another more tightly and fill in the interstices, thereby reducing the porosity of the material.

The compositions of the invention are stable and congeal at about 20 C., depending upon the concentration of wax in the mixture.

Fibrous and cellulosic sheet material can be impregnated with the composition of the invention simply by spraying it, preferably in the form of a fine mist or fog, onto the sheet at ambient or elevated temperature in such manner as to obtain substantially uniform penetration. This can be done in an open room and with or without the application of heat at a temperature preferably above the congealing temperature of the composition, or in a closed treating zone at temperatures as high as 150 to 200 C. While the moisture content of the fibrous sheet material to be treated by the spray method of the invention is not particularly critical, optimum results are obtained with paper and paper board when the relative humidity thereof is fairly low, i.e., of the order of about 5%.- The treatment can also be carried out by immersing the material in the composition, e.g., by passing a continuous web of paper board through a bath of mixture at ambient or elevated temperature.

One very desirable method of treatment involves. the use of a clossed treating zone such as that described in my earlier copending application Serial No. 730,085, referred to earlier, at temperatures of about 90 to 150 C., the paper or paper board being introduced into the closed treating zone at ambient temperature. Generally, somewhat higher temperatures are preferable when the paper to be treated is relatively compact and lower temperatures are desirable when the paper has a less compact structure. However, precautions should be observed, as can readily be determined by trial and error, to avoid having the temperature so high as to damage the material or to penetrate through entire material if it is desired only to treat one side.

The amount of mixture applied to a fibrous sheet material will of course vary depending upon the weight of the material, the grade and texture of the material, the particular formulation employed and the results desired, as will readily be determinable by those skilled in the art.

By way of example, a vaporized mixture of 72% by Weight perchloroethylene, 14% by weight benzene, 12% by weight paraffin wax, 2% by weight pine resin and two drops of castor oil per 1000 grams of mixture can be applied at the rate of 5 kgs. per ton of second grade kraft paper at a temperature of 60 C. with the paper traveling at a speed of 100 meters per minute for a residence time 4 of as little as .06 minute. It is to be understood, of course, that the residence time can be reduced with increased temperature.

By way of further example, a vaporized mixture of 68% by weight trichloroethylene, 18% by weight benzene, 12% by weight paraffin wax, 2% by weight pine resin and two drops of castor oil per kg. of mixture can be applied in substantially the same manner and rate to achieve ap proximately the same results. I

In a further test, the substitution, for pine resin, of about 2% by weight of a short oil, non-oxidizing alkyd resin in the form of a 60% toluol solution, having an acid number of 48 and available under the name Rezyl 99-4-60 was found to be effective.

Corrugated kraft paper board impregnated in the nian= ner described is readily capable of accepting organic inks; shows no significant darkening, and is outstandingly superior in its strength and rigidity retention, even with protracted immersion in water.

It is to be expected that numerous modifications will readily become apparent to those skilled in the art upon reading this description. All such modifications are in-' tended to be included within the scope of the invention as defined in the appended claims.

I claim: p I g i v 1. A composition consisting essentially of about 70 parts by weight of a chlorinated ethylene, about 16 parts by weight benzene, about 12 parts by Weight paraf fin wax, a minor amount up to about 2 parts by weight vegetable resin as hardener and a trace of castor oil as plasticizer.

2. A method which comprises impregnating cellulosic sheet material with a composition comprising about 40 to 94 parts by weight of a chlorinated ethylene, about 6 to 50 parts by weight benzene, and an amount up to about 22 parts by weight paraflin wax. I

3. A method which consisting essentially of impregnat ing cellulosic sheet material with a composition comprising about 40 to 94 parts by weight of a chlorinated ethylene, about 6 to 50 parts by weight benzene, about 12 parts by Weight paraflin Wax, up to about 2 parts by weight resin as hardener, and a trace of castor oil as plasticizer.

4. Cellulosic sheet material stabilized against moisture; said material having been treated with a composition consisting essentially of about 40 to 94 parts by Weight of a low molecular Weight chlorinated hydrocarbon, about 6 to 50 parts by weight benzene, and an amount up to about 22 parts by weight wax of the group consisting of vegetable and mineral waxes. I

S. Cellulosic sheet material stabilized against moisture, said material having been treated with a composition consisting essentially of about 40 to 94 parts by weight of a chlorinated ethylene, about 6 to 50 parts by weight benzene, and about 12 parts by weight paraidn wax.

6. Cellulosic sheet material stabilized against moisture, said material having been treated with a composition consisting essentially of about 40 to 94 parts by Weight of a chlorinated ethylene, about 6 to 50 parts by weight benzene, about 12 parts by weight paraflin wax, up to about 2 parts by weight vegetable resin as hardener and a trace of castor oil as plasticizer.

7. Cellulosic sheet material stabilized against moisture, said material having been treated with a composition consisting essentially of about 70 parts by weight of a chlorinated ethylene, about 16 parts by weight benzene, about 12 parts by weight paraffin wax, up to about 2 parts by weight vegetable resin as hardener and a trace 70 of castor oil as plasticizer.

group consisting of vegetable and mineral waxes, and a benzene, about 12 parts by weight paralfin wax, about 2 10 parts by weight pine resin as hardener and a trace of castor oil as plasticizer.

11. A method for stabilizing cellulosic sheet material against water which comprises treating said material with a composition consisting essentially of about 40 to 94 parts by weight of a low molecular weight chlorinated hydrocarbon, about 6 to 50 parts by weight benzene, and an amount up to about 22 parts by weight of a wax of the group consisting of vegetable and mineral waxes.

References Cited in the file of this patent UNITED STATES PATENTS 2,015,943 Loges Oct. 1, 1935 2,056,048 Gregory et a1. Sept. 29, 1936 2,646,363 Parmentier July 21, 1953 

8. A COMPOSITION CONSISTING ESSENTIALLY OF ABOUT 40 TO 94 PARTS BY WEIGHT OF A LOW MOLECULAR WEIGHT CHLORINATED HYDROCARBON, ABOUT 6 TO 50 PARTS BY WEIGHT BENZENE, AN AMOUNT UP TO ABOUT 22 PARTS BY WEIGHT OF A WAX OF THE GROUP CONSISTING OF VEGETABLE AND MINERAL WAXES, AND A MINOR AMOUNT UP TO ABOUT 2 PARTS BY WEIGHT OF A VEGETABLE RESIN AS HARDENER. 